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# PLRSEG.H -- Macros for sequentially reading segments of a range list.
#
# plr_init (rl, descriptor)
# npix = plr_nleft (descriptor)
# val = plr_getseg (rl, descriptor, npix, value)
#
# plr_init Initialize descriptor for sequential i/o from the rangelist RL.
# plr_nleft Number of pixels left in the current line segment of constant
# value. Zero is returned at the EOL.
# plr_getseg Read NPIX pixels from the current segment, advancing to the
# next segment automatically when the the current segment is
# exhausted.
#
# The descriptor is an integer array, the contents of which are hidden from
# the application using these macros.
# Range list i/o descriptor.
define LEN_PLRDES 4
define rd_nleft $1[1]
define rd_value $1[2]
define rd_x $1[3]
define rd_rn $1[4]
# PLR_INIT -- Initialize the rangelist descriptor.
define (plr_init, { # $1=rl $2=des
rd_x($2) = 1
rd_rn($2) = RL_FIRST
plr_nextseg ($1, $2)
})
# PLR_NLEFT -- Number of pixels left in the current segment.
define plr_nleft rd_nleft($1)
# PLR_GETSEG -- Read pixels from the current segment.
define (plr_getseg, { # $1=rl $2=des $3=npix $4=value
$4 = rd_value($2)
rd_x($2) = rd_x($2) + $3
rd_nleft($2) = rd_nleft($2) - $3
if (rd_nleft($2) <= 0)
plr_nextseg ($1, $2)
})
# PLR_NEXTSEG -- Set up the next segment (internal routine).
define (plr_nextseg, { # $1=rl $2=des
if (rd_rn($2) <= RL_LEN($1)) {
if ($1[1,rd_rn($2)] > rd_x($2)) {
rd_value($2) = 0
rd_nleft($2) = $1[1,rd_x($2)] - rd_x($2)
} else {
rd_value($2) = $1[3,rd_rn($2)]
rd_nleft($2) = $1[2,rd_rn($2)]
rd_rn($2) = rd_rn($2) + 1
}
} else if (rd_x($2) <= RL_AXLEN($1)) {
rd_value($2) = 0
rd_nleft($2) = RL_AXLEN($1) - rd_x($2) + 1
}
})
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